The present invention relates to a composite magnetic head device for magnetically recording and reproducing information on and from a recording medium by heating it, and an information recording and reproducing device adopting the same and also relates a recording medium.
Recently, various systems which realize high density recording with a combination of the optical technology and the magnetic recording and reproducing technology have been developed, examples of which include a laser assisted magnetic recording and reproducing system. In this magnetic recording and reproducing system, for example, as disclosed in Japanese Unexamined Patent Publication No. 176034/1992 (Tokukaihei 4-176034, published on Jun. 23, 1992), a magnetic recording medium made of a ferrimagnetic material whose compensation temperature is around room temperature is adopted. In this system, a recording operation is performed by heating the recording medium by projecting thereon a laser beam so as to reduce the coercive force of the heated portion. In this state, an external magnetic field is applied to the magnetic recording medium by means of an information recording-use write head, thereby recording information. On the other hand, a reproducing operation is performed by heating the recording medium by projecting thereon a laser beam so as to increase the residual magnetization in a heated portion, and further detecting residual magnetic flux by means of an information reproducing-use read head, thereby reproducing information.
In the foregoing laser assisted magnetic recording and reproducing system, the residual magnetization in a non-heated portion maintained at around room temperature is nearly zero. Therefore, even if the reproducing-use read head width in the crosstalk direction is wider than the track pitch for recording information, it is possible to surely suppress the crosstalk, thereby realizing reproduction of information recorded at high density.
The head structure for the foregoing laser assisted magnetic recording and reproducing system is arranged such that the magnetic head and the optical head are provided opposing one another so as to sandwich a recording medium in between.
However, in the foregoing structure of providing the magnetic head and the optical head separately on opposite sides of the recording medium so as to oppose one another, it is difficult to align the magnetic head and the optical head with desirable conformity, which results in the problem of low productivity. Besides, the foregoing structure is not applicable to both-sided recording medium. Therefore, the foregoing structure hinders an increase in recording capacity. Therefore, the development of a composite structure of the magnetic head and the optical head, which eliminates the need of aligning two heads, and which is applicable to the both-sided recording medium is strongly desired.
In response, various types of such composite structure of the magnetic head and the optical head have been proposed in the fields of magneto-optical recording and the thermomagnetic recording.
For example, (1) Japanese Unexamined Patent Publication No. 273252/1989 (Tokukaihei 1-273252, published on Nov. 1, 1989) discloses a magneto-optical pickup wherein a laser diode and an optical system are incorporated within a magnetic circuit with a spacing. According to the structure of the prior art document (1), the laser emitting section can be matched with the gap of the magnetic head, and therefore a desirable composite structure can be achieved.
(2) Japanese Unexamined Patent Publication No. 189905/1991 (Tokukaihei 3-189905, published on Aug. 19, 1991) discloses a magnetic head device 101 illustrated in FIG. 14, wherein a semiconductor laser 102 and a thin film magnetic head 103 are formed on the same substrate. In this magnetic head device 101, the laser emitting section (semiconductor laser 102) and the thin film magnetic head 103 are formed on the same substrate by the semiconductor manufacturing process. With this structure, a positional displacement between the laser emitting section and the thin film magnetic head 103 can be reduced to around 0.3 xcexcm.
However, recently, a head device of a laminated structure is adopted to be suited for the high density recording, and the foregoing magnetic circuit with a spacing as disclosed by the prior art document (1) which is not suited for the high density recording does not have much demand. It is therefore not practical to adopt the structure of the prior art document (1).
According to the structure of the prior art document (2), the position of the laser emitting section is not matched with the position of the gap 106 of the magnetic head (thin film magnetic head 103). Therefore, when adopting the magnetic head device 101 of the prior art document (2), information are recorded magnetically utilizing thermal distribution on the recording medium 104. Namely, in this document (2), the structure for desirably raising the temperature of the recording medium 104 by a laser beam 105 has not been discussed.
In the foregoing composite structure wherein the magnetic head and the optical head are provided opposing one another so as to sandwich the recording medium in between, any concrete example for the tracking servo system has not been discussed.
Furthermore, the tracking servo system adopted in the foregoing prior art document (2) is disadvantageous in that the polarity of the positional information used in the servo performance reverses track by track, and the solution to this problem has not been discussed.
It is an object of the present invention to provide a composite magnetic head device, an information recording and reproducing device adopting the same and a recording medium suited for the laser assisted magnetic recording and reproducing system.
In order to achieve the above object, a composite magnetic head of the present invention is characterized by including:
a recording head for magnetically recording information on a recording medium,
a reproducing head for magnetically reproducing information from the recording medium; and
heat sources for heating the recording medium when recording and reproducing, the heat sources being provided for the recording head and the reproducing head respectively.
According to the foregoing structure, the heat sources for raising the temperature of the recording medium when recording and reproducing information on and from the recording medium are separately provided for the reproducing head and the recording head respectively, and it is therefore possible to provide each head and a corresponding heat source in close proximity at a shorter distance.
With this arrangement, when recording and reproducing information based on the thermal distribution of the recording medium heated by the heat source, it is not necessary to heat the recording medium excessively in a wide region, and it is therefore possible to suppress a thermal damage on the recording medium. Furthermore, when reproducing by heating a reproducing portion to a predetermined temperature by the reproducing head, such problem that the recording medium is heated too much, and the recorded information is erased can be prevented.